The ontogeny of exploration in the rat: Habituation and effects of handling

Abstract

Exploration, measured by head-dipping in a holeboard, was tested in male rats at 16, 21, 28, 56, and 84 days of age. Headdipping increased with increasing age from Day 16 to Day 84, and so did the number of rears made. At all ages handled rats showed more head-dipping and made more rears than did their unhandled litter-mates. The age differences in exploration cannot be explained by different patterns of habituation: rats showed significant within-session habituation of head-dipping at all ages tested (Days 16, 21, and 28). Day 16 rats also showed significant between-session habituation.